``The statute is applicable to foreign ships in the United States waters to the same extent that it is applicable to American ships in those waters,'' Justice Anthony Kennedy wrote for the majority. He was joined by Justices John Paul Stevens, David H. Souter, Ruth Bader Ginsburg and Stephen G. Breyer.

Still, the ruling is unclear how much the $2.5 billion foreign cruise industry, two-thirds of whose passengers are Americans, will actually have to reconfigure pools, restaurants and emergency equipment for wheelchair accessibility, an upgrade that could cost the industry millions.

That's because Kennedy also writes that cruise lines need not comply with the ADA to the extent it creates too much international discord or disruption of internal affairs, under a provision of the statute that calls only for ``readily achievable'' modifications.

Three disabled passengers, who boarded Norwegian Cruise Line in Houston in 1998 and 1999, say they paid premiums for handicapped-accessible cabins and the assistance of crew but the cruise line failed to configure restaurants, elevators and other facilities in violation of the ADA.

Norwegian Cruise Line countered that only an explicit statement of Congress can justify imposing the U.S. law on a ship that sails under a foreign flag, even if it is docked at a U.S. port. The federal law is silent as to whether foreign cruise lines are covered by the ADA.